Suppose we have the following process tree:

init-> ProcessA->processB->processC

then I kill processB

Who is the parent of the processC?
init or the processA

init will inherit processC.

Thank you, Why is init the parent?

Process A can be expected to keep track of its own children. But it has no idea how many children Process B created. If processes all must inherit grandchildren, great-grandchildren, and so on, then every process must be prepared to reap an unending number of children it knows nothing about. That's a lot to ask of every process. So we ask it only of init.

By the way, some versions of unix have a ptrace() system call intended to be only used by debuggers. Most versions of ptrace can allow a process to adopt another process and become its parent. There are restrictions on this... both processes must be owned by the same uid and the adoptee cannot be suid.

many thanks Perderabo,

Another doubt that I have is: after a child exits or is killed, in my example processB, does it send a SIGCHLD to its parent (in this case processA)?

Please correct me if I am wrong here.

I would guess not, otherwise we wouldn't end up with zombie processes.

If the parent installed a signal handler for SIGCLD, it will get a signal. But the sender is the kernel, not the dead process.